1. Technical Field of the Invention
The present invention relates to an audio network system that connects a variety of audio devices.
2. Description of the Related Art
Conventional technologies for audio signal communication in an audio network system used for PA such as plays and concerts, music production, and private broadcasting include CobraNet™ described in Non-Patent Reference 1, SuperMAC™ described in Non-Patent Reference 2, and EtherSound™ described in Non-Patent Reference 3.
CobraNet is a professional audio network system developed by Peak Audio, Inc (USA). CobraNet provides a technology using the standard Ethernet™ protocol of IEEE802.3u in which uncompressed audio signals and control signals of multiple channels are transmitted through the Ethernet. This technology can transmit sampling data of a sample rate of 48 kHz and 16, 20, and 24 bits and can handle audio signals and control signals in two directions, each having up to 64 channels (i.e., up to 128 channels in two directions). SuperMAC or EtherSound is the same technology for transmitting audio signals over the Ethernet.
Audio devices having a variety of functions such as analog input, analog output, digital input, digital output, mixing, effecting, recording/reproducing, remote control, and a combination of any two of these functions can be optionally connected to an audio network that uses the above technologies.
[Non-Patent Reference 1] www.balcom.co.jp/cobranet.htm
[Non-Patent Reference 2] www.sonyoxford.co.uk/pub/supermac/
[Non-Patent Reference 3] www.ethersound.com/news/getnews.php?enews13key=101
In any conventional audio network, audio transmission is performed according to the Ethernet standard as described above. In the Ethernet standard, the maximum packet size is limited to 1526 bytes.
In the conventional technologies, not only packets of audio data but also packets of control data such as a command, a reply to the command, and level data for meter display can flow on the network. However, when a plurality of packets of the same or different types is permitted to flow on the network, the band used for transmission of audio data is reduced accordingly. Since packets other than audio data also flow on the network, the packets may disrupt transmission of audio data. This is serious in the Ethernet that employs the CSMA/CD method.
In addition, since samples corresponding to a plurality of sampling periods are transmitted by incorporating them into one packet, it takes time to packetize samples into a packet and to reconstruct a packet into samples and circuitry for the packetization and reconstruction is complicated.